As someone mentioned, which I agree is good.... just ready some preset snakes / wings / skull / diamonds / tools icon that can be stuck on the crest ( limit the number of items that can be added ), allowing size / rotation changes. Select own colours... I think it gives good enough variation that it doesn't look bland....

Allowing too much freedom like MSpaint provides too much space for conflicts.
Some ppl just had to choose a picture that resembles some part of human anatomy and when they're banned, they'll claim it's actually a picture of a hamburger or rambutans.... You know how creative ppl can get.